Pine County, MN (NNCNOW.com) - An arrest was made Thursday in the November 19th incident where six envelopes containing an unknown white powder substance were mailed to the Pine County Courthouse causing an evacuation.

The Pine County Sheriff's Office reports that the 45-year-old man is in custody for multiple terrorist and terroristic threat charges.

He was taken into custody Thursday for the envelopes incident as well as what authorities are calling other related crimes.

The six envelopes ended up containing a bacterial agent mixed in with a household powder.

Apparently the envelopes have been linked to an already on-going investigation by sheriff's office investigators.

The sheriff's office states there were multiple incidents that were being investigated over the past seven months regarding the planting of homemade devices constructed to look like explosives or binary explosive devices placed at various locations, presumably, police say, to cause fear.

They have linked these devises to the man in custody.

However, Pine County Chief Deputy Steven Blackwell says they are working on finding a motive.

"We're still figuring that out... mainly cause fear, trying to implicate others, and a little bit of just showing what he can do. And we're still trying to sort through a lot of the information we have, and we're still gathering on him to kind of come up with a real clear motive on why he was doing this," said Chief Deputy Blackwell.

Blackwell says that the explosives were primarily found spread out near the suspect's property, as well as near his neighbors' property.

Each device was similar, but investigators say some were more sophisticated.

They believe the suspect was working towards building a device that would actually explode.

The man is expected to be charged with multiple acts of terrorism, weapons of mass destruction, as well as terroristic threats.